I tried out the countdown timer and had a problem.
The final countdown doesn't go off for me. I have my profile set to Normal.
I have the timer set to 500, Alert 1 set to 400, alert 2 set for 100, and Vibrate and Restore are checked. Alerts 1 and 2 work fine (short vibration), but the final alert does not do anything. It does restore, but no vibration. When I check the Tone option, Alerts 1 and 2 only trigger a tone (no vibrate), but the final alert does sound a tone and vibrates.

I have an 8700g, OS4.1.0.284.

Any thoughts as to why vibrate only doesn't work?

First, there is a stupid bug with the "vibrate only" setting. This is probably what you're describing. It is fixed in the latest update (version 0.5) which I should be uploading some time this morning.

Second, setting Alert 1 to 400 and Alert 2 to 100 wouldn't work with the timer set at 500. The alerts don't have a "seconds" part, so your setting would have Alert 1 sounding at the 4-hour mark, and since the main timer starts at 5 minutes it would never sound. But since you got the short vibration that they make in a "vibrate only" mode, I assume you have them set to 4 and 1, right? Or maybe you had Repeat Every set to 1?

Also, the secondary alerts do not vibrate unless the main alert is "vibrate only". This is a feature, not a bug. The reasoning behind having them "tone only" unless the main alert is "vibrate only", is that you could have the main timer set at (for example) 2 hours, with the repeating alert set to go off every minute, and it would probably not be very good for your device to have it vibrate 120 times in the span of 2 hours. I supposed I could have tone and vibrate settings for each secondary alert, but I didn't want to clutter things up with that many options.

Anyway, the first vibrate problem you described has been fixed in version 0.5. There are a couple of new features as well, so you might want to upgrade when I post it.